The present disclosure relates to a semiconductor structure, and particularly to a photonic modulator having a contact structure employing a same semiconductor material as a gate electrode of a field effect transistor, and methods of manufacturing the same.
A semiconductor waveguide may be employed in microphotonic devices to enable high efficiency long range transmission of light over distances in the micrometer range or in the millimeter range. The semiconductor waveguide typically employs a single crystalline semiconductor material to minimize signal loss due to absorption of light. The semiconductor material in the semiconductor waveguide has a relative high refractive index. For example, silicon and germanium have a refractive index of about 3.45 and about 4.0, respectively. A dielectric material having a lower refractive constant surrounds the semiconductor waveguide so that a total reflection condition is satisfied at the interface between the semiconductor waveguide and the dielectric material for light impinging on the interface at a glancing angle. The semiconductor wave guide may thus be employed to transmit light having a wavelength greater than the wavelength corresponding to the band gap of the semiconductor material. Typically, infrared lights are employed in the semiconductor waveguide.
Many microphotonic devices manipulate the light in the semiconductor waveguide in some way. For example, the light in the semiconductor waveguide may be absorbed, reflected, or induced to change the phase. One method of manipulate the signal in a waveguide is to add a photonic modulator. Addition of the photonic modulator enables change of the phase of the optical signal traveling through the modulator at a different rate per traveling distance than the phase of the optical signal traveling through a waveguide without phase modulation capability.
Integrating photonic components (i.e., waveguides and modulators) with complementary metal semiconductor oxide (CMOS) and bipolar complementary metal semiconductor oxide technologies on silicon substrates can enable on-chip and chip-to-chip optical interconnects. However, integrating photonic components and CMOS and BiCMOS circuitry has been a challenge because different processing steps need to be integrated into a manufacturing process sequence. A method of efficiently integrating manufacturing steps to minimize the number of processing steps and to reduce the processing time and cost is therefore desired.